Rear bench headrests are easy to add.. 
just procure a set of back seat headrests (including the baseplate behind the cushion) 
from any JY late 80's quantum (maybe passat and audis)  

then carefully peel back the fabric on the rear seatbed back, and fasten the mounting plates
add a small hole in the fabric for the posts, and leave the clips out for easy install and removal.. 

Dan stevens
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From:    Christopher Gronski <gronski@GMAIL.COM>
Subject: Re: Nice 2WD Westy on eBay.co.UK

Did you check out that rear z-bench? It has headrests!

Chris